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Meaning of singularity

  1. Nov 16, 2011 #1
    Hi there,
    I need to know why a singularity in astrophysics is called a singularity. I have a general idea about what a singularity is but I am yet to find out which of the more commonplace meanings of the word the originator of this term had in mind when s/he used it in the context of astrophysics. For example, did they intend the word to be associated with peculiarity or oddness or uniqueness or the state or quality of being one of a kind or did they intend it to be associated with the idea of being single or "singular" as in singular nouns? I am aware that the latter suggestion sounds preposterous but the received Turkish equivalent of singularity, tekillik , which I intend to avoid using in translating a book by Lawrence M. Krauss into Turkish, fails to make sense to me except as a grammatical term. So this question is more about etymology than science but I couldn't possibly have asked it at an arts forum.
     
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  3. Nov 16, 2011 #2
  4. Nov 16, 2011 #3
    Thanks for this, Obafgkmrns. So uniqueness or the 'fact of being different from others" is the idea underlying singularity. My suspicion has been confirmed so far. This has a major bearing on how the term singularity is to be translated into any language.
     
  5. Nov 16, 2011 #4

    George Jones

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    Yes.

    I am not sure that there is a completely accepted technical definition of spacetime "singularity".

    Roughly, a spacetime is singular if there is a timelike curve having bounded acceleration that ends after a finite amount of proper time. Singular spacetimes have "edges".

    What does this mean? "timelike curve" means a path that a person (say, Alice) or particle could traverse in a rocket. "bounded acceleration" means that the rocket always has zero or finite acceleration. "ends after a finite amount of proper time" means that after a finite of time elapses on Alice's watch, Alice falls "off of spacetime" and "into the singulairty."

    By the Penrose-Hawking singularity theorems, any "reasonable" classical spacetime must be singular. Very roughly, in any "reasonable" classical spacetime, gravity is so stong that the fabric of spacetime gets ripped, thus creating an "edge".
     
  6. Nov 16, 2011 #5
    Thanks George. Wow, this is cutting "edge" science. I should be hanging around more here. Best.
     
  7. Nov 22, 2011 #6
    In space a singularity is something that's concentrated to a point. common examples are that of the big bang and black holes.
     
  8. Nov 22, 2011 #7
    Thanks for the input, Said. In saying this, are you taking issue with the argument that "singularity" is etymologically associated with "oddness" or "anomaly" and saying that it is more properly connected with the idea of "being only one," as "singular" is defined in the American Heritage Dictionary? If this is the case, can you confirm whether your notion of the etymological sense of singularity is consistent with the definition of singularity as "a location where gravity goes so mad that space and time become indistinguishable. From general relativity, we know that this is a location where the structure of spacetime becomes singular (hence the name singularity)."
     
  9. Nov 22, 2011 #8

    phinds

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    I would not argue w/ any of the preceding comments, but I'm puzzled why no one has mentioned another meaning of "singularity" as it applies to physics and that is "a place where our math model of reality breaks down and we don't have a clue what's REALLY going on".

    I think that definition (along with others above) applies well to both the Big Bang singularity and to black hole singularities.
     
  10. Nov 22, 2011 #9
    Quite Basicaly Mhozdag, "a location where gravity is so mad that space and time become indistinguishable" is a very good explanation on how a singulairty behaves (ones in black holes or the big bang)
     
  11. Nov 22, 2011 #10

    phinds

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    Since we have no idea what happens at the singularities, I think you should clarify that this is your opinion, not something that is based in current physics.
     
  12. Nov 22, 2011 #11

    Chronos

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    Most scientists consider gravitational singularities unphysical - a mathematical artifact of theory. So far as we know, there is nothing to prevent a singularity from forming once the pauli exclusion limit is exceeded. The key here is 'so far as we know'. Exploring the consequences of density in this range is a difficult challenge. What we do know is an event horizon can form without a singularity, all you need to do is compress mass to a volume less than its schwarzschild radius. Is there a natural limit to the amount of compression possible? I would hazaard to guess it cannot exceed the planck density.
     
  13. Nov 23, 2011 #12
    Closer to the second, one example of a mathematical singularity is 1/x. You have a smooth function everyone except at x=0, and that's a singular point.

    Incidentally, the standard Chinese translation of "singularity" is qi (strange) dian (point).
     
  14. Nov 23, 2011 #13

    Drakkith

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    Given that matter goes through stages of degeneracy as the pressure increases, from white dwarfs to neutron stars to black holes, would it be unreasonable to assume that black holes cause the most massive particles to form and remain stable, similar to neutrons inside a neutron star?
     
  15. Nov 23, 2011 #14
    Can you somehow explain how your understanding of mathematical singularity would apply to "technological singularity," which "refers to the hypothetical future emergence of greater-than-human intelligence through technological means" or "an intellectual event horizon, beyond which the future becomes difficult to understand or predict." (Wikipedia, italics mine) (If a mathematical singularity is "in general a point at which a given mathematical object is not defined, or a point of an exceptional set where it fails to be well-behaved in some particular way" [Wikipedia, italics mine] and if a spacetime singularity refers to a location where the known laws of physics break down, then singularity would appear to be synonymous with "anomaly," "twilight zone," "abnormality," "aberration," etc rather than with the opposite of "plurality." Am I entirely wrong?)
     
  16. Nov 25, 2011 #15
    I don't believe any singularity can form in a black hole for the simple reason that when the radius of the collapsing star nears that of its event horizon time gets warped to such a degree that the collapse itself stops. It would take more than an infinite time to shrink to a singularity.
     
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